Control And Assembly Of Polyoxometalate-based Metal-organic Frameworks With Schiff Base Complexes

The design and synthesis of metal-organic frameworks (MOFs) has attracted great attention in recent years, because of potential applications such as heterogeneous catalysis, separation and ion exchange. A successful synthetic strategy to prepare polyoxometalate-based metal-organic frameworks involves the combination of the organic ligands, polyoxoanions and metal ions. On the basis of molecule design and assembly, ten new compounds have been constructed by combining polyoxometalates and Schiff ligands with suitable metal ions. These compounds were characterized by IR, elemental analysis, TG technique and X-ray crystallography. The luminescent properties of the compounds in the solid state were investigated.(I) The POM-based helical compound [(AgL1)2(PMo₁₂O₄₀)](AgL1)(PMo₁₂O₄₀)(DMF)4 (1) with pore dimensions of 19.8×5.9 ? was synthesized from the ligand L1 (L1 = 1,4-diphenyl-1,4-bis(2-pyridyl)-2,3-diaza-1,3-butadiene), AgNO3 and [PMo₁₂O₄₀]3–.(II) Three POM-based containing silver(I) double-helicates compounds [(AgL²₂)2(HPW₁₂O₄₀)] (2), [(AgL²₂)2(HPMo₁₂O₄₀)](H2O)4 (3) and [(AgL²₂)2(SiMo₁₂O₄₀)](DMF)5 (4) have been synthesized with polyoxometalates ([PW₁₂O₄₀]3–, [PMo₁₂O₄₀]3– and [SiMo₁₂O₄₀]4–), AgNO3 and the Schiff-base ligand L2 (L2 = 2,5-bis(2-pyridyl)-3,4-diaza-2,4-hexadiene), respectively.(III) One dimension chain POM-based containing silver(I) coordination compounds {[Ag3L33](PW₁₂O₄₀)(CH₃CN)(HONCH₃CH₃)2.5}n (5), two POM-based containing silver(I) [Ag2L31.5(CH₃CN)2][AgL30.5(CH₃CN)2](PMo₁₂O₄₀) (6) and [(SiMo₁₂O₄₀)(Ag2L3(CH₃CN)3)2](CH₃CN)2 (7) have been synthesized with polyoxometalates ([PW₁₂O₄₀]3–, [PMo₁₂O₄₀]3– and [SiMo₁₂O₄₀]4–), AgNO3 and the Schiff-base ligand(L3 = 1,4-bis(2-pyridyl)-2,3-diaza-1,3-butadiene);(IV) Two porous coordination polymers based on Keggin anions, {[Ag1.5L4(H2O)0.5(MeOH)0.5](AgL4)0.5[(AgL4)(PW₁₂O₄₀)](H2O)2.5(MeOH)0.5}n (8) with pore dimensions of 6.8×14.4 ? and {[(AgL4)2(PMo₁₂O₄₀)](AgL4)(CH₃CN)2(HONCH₃CH₃)}n (9) with pore dimensions of 9.5×5.3 ?, were synthesized from the ligand L4 (L4 = 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene) with AgNO3 and [[PX12O40]3– (X = MoVI, WVI).(V) A porous coordination polymers based on Keggin anion {[(Ag2L52)(PMo₁₂O₄₀)](AgL52)(CH₃CN)2(HOCNCH₃CH₃)2.5}n (10) with pore dimensions of 12.9×6.6 ? was synthesized from L5 (L5 = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene), AgNO3 and [PMo₁₂O₄₀]3–.